In subterranean well completions, of both surface and subsea types, a metal tubing structure such as production tubing is typically supported from an appropriate metal hanger structure and extends downwardly therefrom through the wellbore portion of the completion which is normally lined with a metal casing structure. It is often desirable to monitor the state of various downhole well parameters such as, for example but not by way of limitation, the temperatures and pressures within the tubing and external to the tubing in an annular space defined between the tubing and the casing. Many times the desired sensing locations for these well parameters are thousands of feet downhole. Thus, signals indicative of the sensed well parameters must correspondingly be tubing wall-transmitted upwardly through great distances via the wellbore (and a lengthy undersea riser in a subsea application) to a predetermined signal receiving location.
Various techniques have previously been proposed for generating and transmitting these well parameter signals. One such technique has been to transmit acoustic signals upwardly through the downhole metal wall portion of the tubing structure and then to the signal receiving location, via the wall portion of the remainder of the tubing structure, for conversion to, for example, digital or analog electrical signals.
A substantial impediment to successfully utilizing this acoustic-based signal transmission technique has been the necessary presence of a metal hanger structure from which the metal tubing structure is supported. In a subsea application, this metal hanger structure is typically a fluted hanger assembly, and in a surface application it is typically a slip structure. In either case, due to the metal-to-metal contact between the hanger structure and the tubing the hanger structure substantially dissipates an acoustic signal reaching it via a downhole portion of the tubing wall.
Accordingly, the acoustic signal reaching the tubing wall section uphole of the hanger structure is substantially weakened. In the case of a subsea well application, this weakened signal may then have to travel thousands of feet upwardly through the tubing wall above the hanger structure to reach the signal receiving location. Thus, the through-tubing acoustic transmission of downhole well parameter signals to a signal receiving location uphole of the well completion hanger structure has proven difficult, and in many applications unfeasible, to implement. A need thus exists for an improved acoustic-based signal transmission system in a well completion. A need additionally exists to transmit acoustical signals downwardly past the hanger structure, to a downhole location, to actuate devices and reconfigure acoustic transmission devices for better communications.